WO 00/34958 discloses a conventional substantially circular electron beam emitter. The emitter generally comprises a closed vacuum chamber with an exit window and an electron source inside the chamber. The electron source in this disclosure is a filament. By conducting a current through the filament, the filament is heated to about 2000° C. and emits a cloud of electrons. These electrons are then accelerated in vacuum from the filament to the exit window by a voltage difference between the filament and the exit window. The energy of the electrons as they leave the chamber through the exit window can e.g. be used to cure coatings on webs moving past the emitter and for sterilisation of surfaces.
However, there exist a number of different kinds of emitters using different kinds of technology to achieve the desired electron beam. See e.g. U.S. Pat. Nos. 5,962,995 and 5,637,953.
Furthermore, U.S. Pat. No. 5,194,742 discloses a method of and apparatus for shielding electron and other particle beam accelerators. The disclosed design relates to a tunnel-shaped shielding, through which the web is guided, and an emitter fastened to the wall of the shielding. The specific feature of this design is that a portion of the shielding is movable in a direction transverse to both the electron beam and the travel direction of the web, with the purpose of facilitating threading of the web through the tunnel.